Field of the Invention
The present invention relates to a semiconductor device having a termination region for electric power conversion.
Description of the Background Art
Power devices, which are semiconductor devices for electric power conversion, are widely used in various fields from home electric appliances, electric vehicles, railroads, to attention-getting renewable energy, such as photovoltaic power generation and wind power generation. In such fields, power devices or power electronics apparatuses equipped with the power devices are used for conversion of electric power energy. Higher performance, such as reduction in size and higher efficiency, has been desired.
A power device includes an element region provided in a center of a chip and a termination region provided in a peripheral portion of the element region. The element region primarily passes electric current. The termination region has a breakdown voltage. Although the termination region serves as a region for determining a breakdown voltage characteristic that is one of important characteristics of the power device, it is desirable to design the termination region as small as possible to make a smaller chip because the termination region is inactive while energized.
In order to satisfy the above-described requirements, some power devices have begun employing a reduced surface field (RESURF) structure and a variation of lateral doping (VLD) structure that allow the termination region to be smaller than that of a guard ring (GR) structure generally used until now.
The termination region provided in the power chip includes a straight portion and a corner portion. When the straight portion and the corner portion are designed with common structure, the nature of the corner portion having a curvature causes a problem that an electric field concentrates more easily in the corner portion than in the straight portion.
Various structures for relaxing concentration of the electric field in the corner portion have conventionally been proposed to solve the above-described problem. For example, a structure is disclosed to relax concentration of the electric field in the corner portion by making a breakdown voltage holding region formed in the corner portion wider than the breakdown voltage holding region formed in the straight portion (that is, by enlarging an area of the corner portion in the termination region). (For example, refer to Japanese Patent Application Laid-Open No. 2009-164486.)